Most pubs and bars offer some non-alcoholic drinks (for designated drivers, those who don't drink, etc.). As someone who doesn't drink alcohol at all, I have never found it an issue on my travels. Usual options are orange or other fruit juice, lemonade, cola, iced tea, sometimes tea or coffee.
If you need an excuse for not drinking, some meds react with alcohol, or you should be able to say that drinking is just not your thing. Most people will accept that.
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The optimist says the glass is half full.
The pessimist says the glass is half empty.
I just want to know who drank the water...